From Wiktionary, the free dictionary
Literally: “by much”.
بكثير • (bi-kaṯīr[in])
- much, a lot, by far (used with elative adjectives with a comparative sense)
هٰذَا أَكْبَرُ مِن ذٰلِكَ بِكَثِير.- hāḏā ʔakbaru min ḏālika bikaṯīr.
- This one is much bigger than that.